JPS6017425A - Liquid crystal display device - Google Patents

Abstract

PURPOSE:To prevent the breaking of each electrode pattern at the sealed part by holding a liq. crystal between plastic substrates each having the electrode pattern and an orienting film, and extending the orienting film to the peripheral part of the substrate to be sealed. CONSTITUTION:A liq. crystal display element is manufactured using polyethylene terephthalate films each having an electrically conductive transparent film formed thereon as substrates 1, 2. At this time, polyether amide resin films as orienting films 8 are formed on the substrates each having an electrode pattern so that the films 8 reach the peripheral parts for sealing shown by a broken line. Polarizing plates 5, 6 may be placed at the outsides of the substrates 1, 2, yet since plastic substrates are used, it is preferable that substrates 11, 12 which double as polarizing plates are used to simplify the structure.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a liquid crystal display device using a plastic substrate.

[Background of the invention]

Conventionally, liquid crystal display elements have been constructed by sandwiching the liquid crystal between two glass substrates (upper and lower) with electrodes formed on their inner surfaces, and sealing the periphery with a sealant. However, in recent years, glass substrates have been replaced. A model using a plastic substrate has been announced.

FIG. 1 shows an example of the configuration of this type of liquid crystal display device.

This is an example of the so-called twisted nematic type. In the figure, 1 and 2 are upper and lower substrates made of plastic films such as biaxially stretched polyethylene terephthalate (hereinafter abbreviated as PET), and the surroundings are It is bonded with a sealing material 3, and a liquid crystal 4 is sealed inside. An upper polarizing plate 5 and a lower polarizing plate 6 are arranged on the outside of these substrates 1 and 2, respectively, and a reflective film T is further laminated on the outside of the lower polarizing plate 6.

In liquid crystal display devices using such plastic substrates, when forming a transparent conductive film (hereinafter abbreviated as ITO film), it is not possible to raise the firing temperature sufficiently, so sufficient adhesion strength cannot be obtained. The problem is that there is no.

That is, although not shown in the figure, electrodes made of an ITO film having a predetermined pattern are provided on the inner surfaces of the substrates 1 and 2 in order to obtain a desired display pattern.

This is usually done by forming an ITO film on the entire surface of the substrate and then etching it. However, when forming this thicker ITO film, it takes 400 to
While it is possible to fire at 450 t:',
In the case of a device using a plastic substrate, it is necessary to suppress the heat distortion temperature of the plastic to below (approximately 150 C). For this reason, an ITO film formed on a plastic surface has lower physical strength than one formed on a glass surface, and if you rub both film surfaces strongly with an eraser, for example, you will notice that only the ITO film on the plastic surface is strong. This can also be confirmed from phenomena such as peeling off.

In liquid crystal display elements using such plastic substrates, the strength of the ITO film is not sufficient, whereas in the peripheral sealing parts of the upper and lower substrates, the electrode pattern made of the ITO film and the sealing material 3 directly contact each other. Therefore, experimental results have been obtained that stress is applied to the electrode pattern due to deformation of the sealing material 3 due to thermal expansion, etc., and the incidence of wire breakage increases.

[Purpose of the invention]

The present invention was made in view of these circumstances, and
The purpose is to provide a liquid crystal display device in which disconnection of the electrode pattern at the seal portion is prevented.

[Summary of the invention]

In order to achieve such an object, the present invention extends the alignment film to the sealing portion.

In other words, in order to alleviate the stress generated in the electrode pattern due to the influence of the sealant, and to prevent the electrode pattern from being directly affected by the chemical influence of the sealant, it is possible to interpose a thin organic film between the two. The process is simplified by using, as this organic film, an alignment film formed to align the directions of liquid crystal molecules on the substrate surface.

[Embodiments of the invention]

An ITO film was formed on a PET film having a thickness of 0.2 mra, and then etched to form an electrode pattern. Using these as substrates 1 and 2, a liquid crystal display element having the configuration shown in Fig. 1 was created. did. At that time, a film made of polyetheramide resin was formed as an alignment film on the substrate on which the electrode pattern was formed, but normally the alignment film 8 covers only the display area with respect to the wL electrode pattern, as shown by diagonal lines in FIG. In contrast, as shown in FIG. 3, the alignment film 8 was arranged so as to cover the peripheral sealing portion indicated by the broken line.

The element thus created was subjected to a durability test for 500 hours in an atmosphere of 1.95% RH (7), and the incidence of wire breakage due to the influence of the sealant 3 was less than 0.1%9. This could be reduced to 1/1o compared to the conventional method.

In the above-described embodiment, the polarizing plates 5 and 6 were arranged separately on the outside of the substrates 1 and 2, but since plastic substrates are used, it is easy to use both of them to simplify the structure.

FIG. 4 shows such an example. In other words, 1 in the figure
1 is an upper polarizing substrate, and 12 is a lower polarizing substrate. As shown in FIG. 5, these have a structure in which a polarizer 14 is sandwiched between two supports 130 made of uniaxially stretched PET film, and serve as a substrate constituting a liquid crystal cell as well as a polarizing plate. ing. Therefore, no other polarizing plate is required, and the reflecting plate 1 is placed directly outside the lower polarizing substrate 12. In addition, in FIG. 5, an arrow 15 indicates the stretching direction of PET.

In this embodiment, after forming an electrode pattern 9 made of an ITO film, an alignment film is applied to a sealing material 3 in the same manner as shown in FIG.
After the bonding was completed up to the 0 portion, orientation treatment was performed using a rubbing method, and the incidence of wire breakage due to the sealing material 3 could be similarly reduced.

[Effects of the Invention] As explained above, according to the present invention, although the alignment film is extended to the sealing part, the electrode pattern made of the ITO film is prevented from directly touching the sealing material. It is possible to alleviate the physical or chemical influence from the sealing material and significantly reduce the wire breakage rate.

[Brief explanation of the drawing]

Fig. 1 is a cross-sectional view of a liquid crystal display device using a conventional plastic substrate, Fig. 2 is a plan view showing the state of formation of a conventional alignment film, and Fig. 3 shows a state of formation of an alignment film in the present invention. 4 is a plan view, FIG. 4 is a sectional view showing an embodiment of the present invention, and FIG. 5 is a detailed view showing the structure of the substrate. 1.2...Fist board, 3...φ sealing material, 4...
Liquid crystal, 8... alignment film, 9 nose... electrode pattern, i
t, 12...Substrate that also serves as a polarizing plate, 13...P
Support consisting of ET, 14...Polarizer.

Claims (1)

[Scope of Claims] 1. A liquid crystal is sandwiched between two upper and lower substrates made of plastic, with an electrode pattern and an alignment film made of a transparent conductive film on the inner surface, and the periphery is sealed with a sealant. 1. A liquid crystal display device characterized in that an alignment film extends to a sealed portion around a substrate. 2. The liquid crystal display device according to claim 1, wherein a polarizing plate having a support made of polyethylene terephthalate is used as the substrate.